(a) Field of the Invention
The present invention relates to a thin film array panel and a manufacturing method thereof.
(b) Description of the Related Art
Generally, a thin film array panel is used for display devices such as liquid crystal displays (LCDs) and organic light emitting displays (OLED).
The LCD is one of the most widely used flat panel displays since it is lightweight and occupies less space than conventional cathode ray tube (CRT) displays. The general structure of an LCD consists of a liquid crystal (LC) layer that is positioned between a pair of panels including field generating electrodes and polarizers. The LC layer is subjected to an electric field generated by the electrodes and variations in the field strength change the molecular orientation of the LC layer. For example, upon application of an electric field, the molecules of the LC layer change their orientation to change the polarization of light passing through the LC layer. Appropriately positioned polarizing filters selectively block the polarized light, creating dark areas that can represent desired images.
The thin film array panel for display device generally includes a plurality of pixel electrodes, a plurality of thin film transistors (TFTs) for controlling signals to be applied to the pixel electrodes, and a plurality of signal lines transmitting the signals and connected to external devices.
An aperture ratio is a significant factor of the LCD since it is related to the luminance of the LCD. The aperture ratio is generally increased by maximizing the size of the pixel electrodes such that the pixel electrodes overlap the signal lines with a passivation layer interposed. The passivation layer is made of organic material having low permittivity and has a thickness equal to about 3 microns in order to reduce the capacitive coupling between the pixel electrodes and the signal lines.
However, the thick passivation layer makes steep height difference at contacts between the signal lines and the external devices, which may cause the defect in the contacts and deteriorate the reliability of the contacts.